Most aircraft have landing gear with a plurality of undercarriages having the essential functions firstly of absorbing a large portion of the kinetic energy due to the vertical component of the speed of the aircraft on landing, and secondly of enabling the aircraft to travel on the ground, in particular during the braking stage to which the present invention relates.
A distinction is generally made between so-called “main” landing gear that supports the major portion of the weight of the aircraft, and so-called “auxiliary” landing gear that serves to balance the aircraft on the ground and to make it more maneuverable. On most modern aircraft, the main landing gear is situated close to the center of gravity of the airplane under the wing or under the fuselage, while the auxiliary landing gear is situated under the nose of the aircraft.
Landing gear generally includes shock absorbers for absorbing energy when the airplane impacts the ground and for ensuring passenger comfort while running on the ground, together with at least one wheel and braking elements, with braking elements usually being mounted solely on the “main” landing gear.
Aircraft braking systems include braking actuators (which may be hydraulic or electromechanical) that are controlled to apply braking torque to the wheels of the aircraft, tending to slow it down.
Most braking controls known in aviation make use of a general setpoint for torque, force, or position, with that being translated either into a pressure for hydraulic brakes, or into a force that is to be applied or into a movement of a pusher for brakes having electromechanical actuators.
At the beginning of braking, the deceleration created by the braking force induces an inertial force on the wheels that causes the aircraft to tilt forwards about a “pitch” axis of the aircraft. This tilting has the consequence of compressing the shock absorber of the auxiliary landing gear.
At the end of braking, when the aircraft comes completely to rest, the shock absorber of the auxiliary landing gear relaxes and thereby causes the aircraft to tilt once more, this time rearwards about the pitch axis.
These tilting movements are phenomena that are particularly uncomfortable for the passengers of the airplane.